The study adds to growing evidence that CFS is caused by a malfunctioning immune system, lead author Mady Hornig, MD, told HealthDay. She is director of Translational Research at the Jerome L. and Dawn Greene Infectious Disease Laboratory at Columbia University's Mailman School of Public Health in New York City. The new study relied on data gathered during two large U.S. studies of CFS, involving 298 people diagnosed with CFS and 348 healthy control subjects. As part of these studies, participants provided blood samples. Researchers analyzed the blood sample data, looking at the presence of cells and chemicals related to the immune system.

The investigators noted that distinct increases occurred in the cytokine levels of people who'd been diagnosed with CFS for fewer than three years, compared with both the healthy controls and people with long-term CFS. The changes are only present early on in the course of disease, and don't appear in long-term patients. The results indicate that there are stages of CFS, and that new patients likely need treatments different from those who have had CFS for a long time, Hornig said.

"It may be possible to prevent the long-term consequences of this illness by intervening early and dampening down these cytokines," Hornig explained. "It also has implications for the very large population of people who have had this disease for a long time and for whom a different strategy may be important."